1. Field of the Invention
The present invention relates to an operation mode detection device to detect the operation mode position in the driving mechanism which drives and controls the tape cassette loading and the tape running statuses, such as recording, playing, fast forwarding, rewinding and stop of the magnetic tape in the magnetic recording and reproducing apparatus, and particularly, to a switch structure which enables cleaning of the contact members in the piano-touch type switch used as the operation mode detection device.
2. Description of the Related Art
A magnetic recording and reproducing apparatus (hereinafter referred to as "VTR (Video Tape Recorder)") carries a tape cassette into the VTR, guides the magnetic tape in the tape cassette to a certain tape running mechanism and the circumference of a cylinder incorporating a rotary head and, according to various operations input from the input means of the VTR, runs the magnetic tape corresponding to the recording, playing, fast forwarding, rewinding or stop mode.
The VTR mechanism which arranges the tape cassette carrying and the magnetic tape running mode is described below with referring to the plan view of FIG. 4 showing a magnetic tape driving mechanism of the VTR. FIG. 4 shows the magnetic tape driving mechanism laid out on the back of the VTR chassis only. The driving mechanism comprises a plurality of mechanism members 31 to 55.
In the figure, on the right side of a chassis 31 in which the magnetic tape driving mechanism of the VTR is placed, an electric motor 32 serving as the driving source is provided. The electric motor 32 is controlled by the operation mode setting means (not shown) for its revolution speed, number of revolutions and revolution direction. Mounted and fixed to the rotational axis of the electric motor 32 is a worm gear 33, which makes rotations coaxially with the rotational axis of the electric motor 32. A first gear 34 is engaged with the worm gear 33. The first gear 34 consists of a large diameter gear 34a engaged with the worm gear 33 above and a small diameter gear 34b coaxial with the large diameter gear 34a. Engaged with the small diameter gear 34b of the first gear 34 is a second gear 35. A bevel gear (not shown) is formed on the flat surface of the second gear 35. Engaged with the bevel gear on the second gear 35 is a large diameter gear 36a of a third gear 36. The third gear 36 comprises the large diameter gear 36a and a small diameter gear 36b coaxial with it. Engaged with the small diameter gear 36b of the third gear 36 is a large diameter gear 37a of a detection gear 37. The detection gear 37 comprises the large diameter gear 37a and a small diameter gear 37b coaxial with it. The small diameter gear 37b of the detection gear 37 is configured as a pinion and is engaged with a first rack 39 linearly formed at an end of a slider 38.
In other words, the rotational driving of the electric motor 32 is reduced by the worm gear 33, the first gear 34, the second gear 35, the third gear 36 and the detection gear 37 and transmitted to the first rack 39 and slides the slider 38 in the horizontal direction shown with an arrow in the figure.
Formed on the slider 38 are a sliding guide groove 40 to guide the linear sliding in the horizontal direction, a first guide groove 41, a second guide groove 42, and a third guide groove 43. With the guide grooves 40 to 43, guide posts 40' to 43' are mated allowing sliding. The guide post 40' is fixed to the chassis 31. Though details are not shown for the remaining guide posts 41' to 43', the guide post 41', for example is provided with a pinch roller driving lever. When the slider 38 makes sliding operation, the pinch roller driving lever is moved corresponding to the shape of the first guide groove 41 so that the magnetic tape is held between the rotational axis (capstan) of a capstan motor 52 to be described later and the pinch roller so that it can run. Further, the guide post 42' of the second guide groove 42, for example, drives a reel base brake (not shown) and the guide post 43' of the third guide groove 43 is, for example, a driving post to drive the tension lever for tape tension adjustment. The guide grooves 41 to 43 and the guide posts 41' to 43' are not limited to the above functions and they may have other functions. The second gear 35 also works to drive the cassette transfer mechanism for driving the cassette frame on which a tape cassette is placed (not shown) between the tape cassette load/unload position and the reel base position provided on the chassis 31.
At the other end of the slider 38, a second linearly formed rack 44 is provided. A small diameter gear 45a configured as a pinion to be engaged with the second rack 44 and a fourth gear 45 having a large diameter gear 45b coaxial with the small diameter gear 45a are also laid out there. Engaged with the large diameter gear 45b of the fourth gear 45 is a loading gear 46a, with which the other loading gear 46b is engaged. To the rotational axes of the loading gears 46a and 46b, fixed arms 47a and 47b are mounted and fixed so that the fixed arms 47a and 47b make rotations in the circumferential direction together with the rotations of the loading gears 46a and 46b. At the ends of the fixed arms 47a and 47b, an end of a swing arm 48a and an end of a swing arm 48b are rotatably mounted respectively. On the other ends of the swing arms 48a and 48b, magnetic tape pull-out poles 49a and 49b are planted toward the surface of the chassis 31 (toward the back of the figure) respectively. These magnetic tape pull-out poles 49a and 49b make sliding guided by loading guide grooves 50a and 50b formed on the chassis 31. Placed at the center of the loading guide grooves 50a and 50b, a cylinder 51 on which the magnetic tape is to be wound.
In other words, when the electric motor 32 makes rotations for driving and slides the slider 38, the fourth gear 45 engaged with the second rack 44 makes rotations and the loading gear 46a engaged with the fourth gear 45 makes rotations clockwise in the figure, and the loading gear 46b engaged with the loading gear 46a makes rotations counterclockwise in the figure. This causes the fixed arms 47a and 47b to make rotations clockwise and counterclockwise. The rotations of these fixed arms 47a and 47b lead the magnetic tape pull-out poles 49a and 49b at the end of the swing arms 48a and 48b to make sliding guided by the loading guide grooves 50a and 50b. In this procedure, the magnetic tape of the tape cassette (not shown) is pulled out by the magnetic tape pull-out poles 49a and 49b and wound on the cylinder 51.
Reference numeral 52 in FIG. 4 indicates a capstan motor, whose revolution speed, number of revolutions and revolution direction are controlled by operation mode setting means (not shown). This is the driving source which drives the magnetic tape to run and drives the reel base of the tape cassette to make rotations. A small diameter belt pulley 53 is fixed to the rotational axis of the capstan motor 52 and a belt 54 is stretched on the belt pulley 53. The rotational driving of the capstan motor 52 is transmitted to a reel base driving belt pulley 55 by the belt 54. The reel base driving belt pulley 55 provides the rotational driving to either the tape feeding reel base or the tape winding reel base of the tape cassette (not shown) corresponding to the operation mode.
In short, when the magnetic tape driving mechanism of FIG. 4 carries and puts the tape cassette to the certain position on the chassis 31, the rotational driving of the electric motor 32 causes the second gear 35 to make rotations, which drives the tape cassette transfer mechanism (not shown). Thus, the cassette is placed onto the reel base, the magnetic tape is pulled out by the loading poles 49a and 49b from the tape cassette placed on the reel base and wound onto the cylinder 51. Further, the rotational driving of the electric motor 32 slides the slider 38 so as to adjust the speed of the running tape and stop the tape by driving the reel base brake to brake the reel base by the second guide groove 42 and the guide post 42', to press the pinch roller against the capstan by driving the pinch roller driving lever with the first guide groove 41 and the first guide post 41', or to drive the tension lever (not shown) using the third guide groove 43 and the third guide post 43', so that various operation modes of the VTR can be set.
Thus, the currently set operation mode can be learned by detecting the sliding position of the slider 38. Further, when this operation mode changes to a next operation mode, the required sliding amount and traveling direction of the slider 38 (Number of revolutions and revolution direction of the electric motor 32) can be learned. To detect the operation mode position where the slider 38 currently is, the rotations of the electric motor 32 are transmitted, via the first to third gears 34 to 36, to the detection gear 37, which slides the slider 38, and the rotation position of the detection gear 37 can be detected by a device 56 provided on the detection gear 37.
Referring to FIG. 5, the configuration of the device 56 is described below. FIG. 5 shows the outline of the detection gear 37 and the device 56.
The surface of the large diameter gear 37a in the detection gear 37 is provided with a circumferential groove 37d around a rotational axis 37c and a circular hole 37e is formed to the flat plane at the outer periphery of the circumferential groove 37d.
On the other hand, the device 56 comprises a rotor section 57, a stator section 58 and a terminal section 59 connected to the stator section 58. Projected at the center of the surface on the rotor section 57 is, a cylinder 57a to be mated with the rotational axis 37c of the detection gear 37. The rotor section 57 is further provided on its surface with a pillar 57b at the position corresponding to the hole 37e of the detection gear 37 so that the pillar 57b can be inserted into the hole 37e.
Specifically, when the central cylinder 57a of the rotor section 57 is mated with the rotational axis 37c of the detection gear 37 and the pillar 57b of the rotor section 57 is inserted into the circular hole 37e of the detection gear 37, the rotor section 57 makes rotations together with the rotations of the detection gear 37.
Next, referring to FIG. 6, detailed configuration of the device 56 is described. FIG. 6(a) is a perspective view showing the surface of the rotor section 57, FIG. 6(b) is a perspective view showing the back (inside) of the rotor section 57 and FIG. 6(c) is a perspective view showing the back (inside) of the stator section 58 and the terminal section 59.
As shown in FIGS. 6(a) and 6(b), the rotor section 57 is provided with a disc-shaped projection section 57c on its outer periphery. Further, as shown in FIG. 6(b), the central cylinder 57a extended from the surface is formed on the back (inside) of the rotor section 57 and a plurality of movable contact member pressure projections 61a to 61d to be pressed against a plurality of switches 62a to 62d laid out on the stator section 58 (to be described later) is formed on circumferences with different diameters around the central cylinder 57a. The movable contact member pressure projections 61a to 61d are positioned so that, when the rotor section 57 makes a rotation together with the rotation of the detection gear 37, they can turn on and off the switches 62a to 62d of the stator section 58 corresponding to the angle of such rotation.
Referring next to FIG. 6(c), the stator section 58 and the terminal section 59 are described. Planted at the center of the stator section 58 is a central axis 5a, with which the central cylinder 57a of the rotor section 57 is to be mated. On the plane around the central axis 58a, four switches 62a, 62b, 62c and 62d are laid out at positions in different distances from the central axis 5a.
The switches 62a to 62d comprise movable contact members 62a' to 62d' and fixed contact members 62a" to 62d" respectively. The movable contact members 62a' to 62d' are commonly connected with a common connection conductor 63 and at the same time fixed to the plane on the inside of the stator section 58. The fixed contact members 62a" to 62d" of the switches 62a to 62d are, via the conductors led to the terminal section 59, connected to the connection terminals 64a to 64d and further connected to the control circuit (with reference numeral 70 in FIG. 7) for operation mode detection.
FIG. 7 shows an example of the circuit configuration for the device 56 in FIGS. 6(a) to 6(c). Among the connection terminals 64a to 64d of the terminal section 59, the terminals 64a to 64c are detection terminals to detect ON or OFF of the switches 62a to 62c and the terminal 64d is a common terminal (grounding terminal) and is connected to the reference potential (to the chassis 31 shown in FIG. 4). The movable contact member for detection terminal 62a' and the fixed contact member for detection terminal 62a" constitute the switch 62a and the movable contact member for detection terminal 62b' and the fixed contact member for detection terminal 62b" constitute the switch 62b, the movable contact member for detection terminal 62c' and the fixed contact member for detection terminal 62c" constitute the switch 62c and the movable contact member for common terminal 62d' and the fixed contact member for common terminal 62d" constitute the switch 62d. The movable contact members 62a' to 62d' are commonly connected by the conductor 63. The fixed contact members 62a" to 62d" are, via the connection terminals 64a to 64d respectively, connected to the control circuit 70, which comprises a microcomputer, for example. As understood from the connection configuration of FIG. 7, the control circuit 70 can detect various operation modes by turning on of at least one of the switches 62a to 62c with the switch 62d turned on, i.e. by combination of the low level of the switch 62d and the low level of at least one of the switches 62a to 62c.
Further, referring to FIGS. 6(a) to 6(c), in order to fix the rotor section 57 rotatably to the stator section 58 after the central cylinder 57a of the rotor section 57 is mated with the central axis 58a of the stator section 58, the stator section 58 is provided with projections 65a to 65c on its outer periphery. The projections 65a to 65c are further provided with fixing pieces 65a' to 65c' to fix the projection section 57c of the rotor 57. Further, the terminal section 59 is provided, on its both end faces, with fixing pieces 66a and 66b to fix the device 56 to the chassis 31 or other casing.
Referring to FIG. 8, the relation between the switches 62a to 62d of the stator section 58 and the movable contact member pressure projections 61a to 61d of the rotor section 57 is described below. FIG. 8 shows a sectional view models of the movable contact member pressure projection 61a and the switch 62a.
Reference numeral 67 in the figure indicates an elastic piece to drive the movable contact member 62a'. It is formed from insulating material and is designed so that its head 67a can contact with the movable contact member pressure projection 61a and the bottom 67b is in contact with the movable contact member 62a'. When the movable contact member pressure projection 61a contacts with the head 67a of the elastic piece 67 and presses down the elastic piece 67 downward of the figure, the movable contact member 62a' is lowered and comes into contact with the fixed contact member 62a". A switch with such a structure is called a piano-touch type switch. For the switch contact members 62a' to 62d' and 62a" to 62d", silver or ordinary metal plates (brass, for example) plated with silver is used.
FIG. 8(a) shows a case where the movable contact member pressure projection 61a of the rotor section 57 is positioned not in contact with the elastic piece 67. In this status, the movable contact member 62a' is at a distance from the fixed contact member 62a" because of the hardness of its material and is not in contact with it, i.e. the switch 62a is in OFF status. When, from this status, the rotor section 57 moves from the right to the left as shown with an arrow in the figure and comes to the position as shown in FIG. 8(b), the movable contact member pressure projection 61a of the rotor section 57 rides onto the head 67a of the elastic piece 67 and presses the movable contact member 62a' downward in the figure so that it comes into contact with the fixed contact member 62a", i.e. the switch is turned on.
Further, when the rotor section 57 makes rotation and the movable contact member pressure projection 61a leaves the head 67a of the elastic piece 67, the movable contact member 62a' leaves the fixed contact member 62a" because of its own elasticity and goes back to the position in FIG. 8(a).
Thus, the rotation of the rotor section 57 in the device 56, together with the rotation of the detection gear 37, detects various operation modes from combination of ON and OFF among the switches 62a to 62d.
In order to detect the operation mode, the switch 62d of the device 56 is used as the common switch (grounding switch connected by the fixed contact member 62d" to the reference potential). In the cassette eject mode where the tape cassette is discharged from VTR and the magnetic tape driving mechanism is in the standby status waiting for loading of a tape cassette, the switches 62a to 62d of the device 56 are turned on and the connection terminals 64a to 64d are, for example, all set to the low level. Then, in the tape loading mode where the tape cassette is carried to the VTR and the magnetic tape is arranged to the cylinder 51 and the rotational axis of the capstan motor 52 of the VTR, the switch 62b and the switch 62d are turned on. Thus, by checking the combination of ON status of the common switch 62d and ON status of other switches 62a to 62c, operation modes including PLAY, STOP, FF(Fast Forwarding), REWIND and REC(Recording) modes are detected.
If, in the VTR provided with an apparatus to detect the operation mode, the VTR operation power is turned off without input of any new operation mode or timer recording is reserved after the tape cassette is put into the VTR and the tape loading mode is completed, some of the switches 62a to 62d in the device 56 are turned off. Until input of the next operation mode or arrival of the recording start time, the VTR continues to be in the standby status. When the standby status is kept long, the switch contact members in OFF status are exposed to the air and react with substances in the air, resulting in sulfurization or oxidation of the surface or dust contamination on the surface. When the VTR proceeds from this standby mode to the next operation mode and the switch in the OFF status is turned on, the above sulfurization, oxidation or dust causes noises. Such noises are supplied from the contact terminals 64a to 64d to the control circuit 70 and lead to erroneous operation in operation mode detection or control of proceeding to the next operation mode.